linux-kernel - RE: [PATCH v16] pwm: opencores: Add PWM driver support

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Message-ID:
 <ZQ0PR01MB1253A5B870FF90900A2643009F02A@ZQ0PR01MB1253.CHNPR01.prod.partner.outlook.cn>
Date: Mon, 23 Dec 2024 02:47:59 +0000
From: William Qiu <william.qiu@...rfivetech.com>
To: Uwe Kleine-König <ukleinek@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>, Hal Feng
	<hal.feng@...rfivetech.com>, Philipp Zabel <p.zabel@...gutronix.de>
Subject: RE: [PATCH v16] pwm: opencores: Add PWM driver support

> -----Original Message-----
> From: Uwe Kleine-König <ukleinek@...nel.org>
> Sent: 2024年12月20日 5:00
> To: William Qiu <william.qiu@...rfivetech.com>
> Cc: linux-kernel@...r.kernel.org; linux-pwm@...r.kernel.org; Hal Feng
> <hal.feng@...rfivetech.com>; Philipp Zabel <p.zabel@...gutronix.de>
> Subject: Re: [PATCH v16] pwm: opencores: Add PWM driver support
> 
> Hello,
> 
> On Mon, Oct 28, 2024 at 09:46:09AM +0800, William Qiu wrote:
> > +static int ocores_pwm_apply(struct pwm_chip *chip,
> > +			    struct pwm_device *pwm,
> > +			    const struct pwm_state *state) {
> > +	struct ocores_pwm_device *ddata = chip_to_ocores(chip);
> > +	u32 ctrl_data = 0;
> > +	u64 period_data, duty_data;
> > +
> > +	if (state->polarity != PWM_POLARITY_INVERSED)
> > +		return -EINVAL;
> > +
> > +	period_data = mul_u64_u32_div(state->period, ddata->clk_rate,
> NSEC_PER_SEC);
> > +	if (!period_data)
> > +		return -EINVAL;
> > +
> > +	if (period_data > U32_MAX)
> > +		period_data = U32_MAX;
> > +
> > +	ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_LRC,
> period_data);
> > +
> > +	duty_data = mul_u64_u32_div(state->duty_cycle, ddata->clk_rate,
> NSEC_PER_SEC);
> > +	if (!duty_data)
> > +		return -EINVAL;
> 
> I can understand that period_data == 0 is an error, but duty_data == 0
> could/should just work?!
> 
It means no need to check whether the duty is valid? 
> > +
> > +	if (duty_data > U32_MAX)
> > +		duty_data = U32_MAX;
> > +
> > +	ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_HRC,
> duty_data);
> > +
> > +	ctrl_data = ocores_pwm_readl(ddata, pwm->hwpwm,
> REG_OCPWM_CTRL);
> > +	if (state->enabled)
> > +		ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_CTRL,
> > +				  ctrl_data | REG_OCPWM_CNTR_EN |
> REG_OCPWM_CNTR_OE);
> > +	else
> > +		ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_CTRL,
> > +				  ctrl_data & ~(REG_OCPWM_CNTR_EN |
> REG_OCPWM_CNTR_OE));
> > +
> > +	return 0;
> > +}
> > [...]
> > +static int ocores_pwm_probe(struct platform_device *pdev) {
> > +	const struct of_device_id *id;
> > +	struct device *dev = &pdev->dev;
> > +	struct ocores_pwm_device *ddata;
> > +	struct pwm_chip *chip;
> > +	struct clk *clk;
> > +	struct reset_control *rst;
> > +	int ret;
> > +
> > +	id = of_device_get_match_data(&pdev->dev);
> > +	if (!id)
> > +		return -ENODEV;
> > +
> > +	chip = devm_pwmchip_alloc(&pdev->dev, 8, sizeof(*ddata));
> > +	if (IS_ERR(chip))
> > +		return -ENOMEM;
> > +
> > +	ddata = chip_to_ocores(chip);
> > +	ddata->data = id->data;
> > +	chip->ops = &ocores_pwm_ops;
> > +
> > +	ddata->regs = devm_platform_ioremap_resource(pdev, 0);
> > +	if (IS_ERR(ddata->regs))
> > +		return dev_err_probe(dev, PTR_ERR(ddata->regs),
> > +				     "Unable to map IO resources\n");
> > +
> > +	clk = devm_clk_get_enabled(dev, NULL);
> > +	if (IS_ERR(clk))
> > +		return dev_err_probe(dev, PTR_ERR(clk),
> > +				     "Unable to get pwm's clock\n");
> > +
> > +	ret = devm_clk_rate_exclusive_get(dev, clk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	rst = devm_reset_control_get_optional_exclusive(dev, NULL);
> > +	if (IS_ERR(rst))
> > +		return dev_err_probe(dev, PTR_ERR(rst),
> > +				     "Unable to get pwm's reset\n");
> > +
> > +	ret = reset_control_deassert(rst);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = devm_add_action_or_reset(dev, ocores_pwm_reset_control_assert,
> rst);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ddata->clk_rate = clk_get_rate(clk);
> > +	if (ddata->clk_rate > NSEC_PER_SEC)
> > +		return -EINVAL;
> 
> Missing error messages for the three checks above.
> 
Will add.
> > +	ret = devm_pwmchip_add(dev, chip);
> > +	if (ret < 0)
> > +		return dev_err_probe(dev, ret, "Could not register PWM chip\n");
> > +
> > +	return 0;
> > +}
> 
> Best regards
> Uwe